Nonadiabatic Effects in Photodissociation of Small Molecules

化学系的理论和计算化学项目支持了托莱多大学郭教授正在进行的关于化学反应中曲线交叉事件的全面调查。郭教授正在对小分子光解的非绝热跃迁动力学进行研究，包括对烷基碘在气相中的光解动力学进行新的三维量子力学计算。郭教授的新方法用量子波包方法处理解离自由度，同时用经典轨迹描述环境运动。量子子系统和经典子系统通过Ehrenfest方案耦合，使得波包和轨道可以自洽地传播。大多数化学反应可以充分理解为包括处于基电子态的反应物和产物分子。然而，有许多重要的反应，包括大多数由紫外线辐射引发的过程，其反应过程涉及基态和激发电子态之间的相互作用。目前正在测试一种新的理论方法，该方法应该能够预测这种过程的概率，从而有助于理解光引发的过程的机制。

The Theoretical and Computational Chemistry Program in the Chemistry Division has supported a comprehensive investigation of curve-crossing events in chemical reactions being carried out by Professor Guo at the University of Toledo. Professor Guo is conducting a study of non-adiabatic transition dynamics in the photodissociation of small molecules, including new three-dimensional quantum mechanical calculations of the photodissociation dynamics of alkyl iodides in the gas phase. Professor Guo's new approach treats the dissociation degree of freedom by a quantum wavepacket method while characterizing environment motions by classical trajectories. The quantum and classical subsystems are coupled via the Ehrenfest scheme so that the wavepacket and the trajectory can be propagated self-consistently. %%% Most chemical reactions can be adequately understood as involving reactant and product molecules in their ground electronic states. However, there are many important reactions, including most processes that are initiated by ultraviolet radiation, for which the reaction process involves interaction between the ground and excited electronic states. A new theoretical method is being tested that should permit prediction of the probability of such processes and thereby contribute to the understanding of the mechanisms of processes initiated by light.